Note that there are several cases when APCu cache does not persist and all set values are lost after PHP process exists. E.g. PHP CLI - successive CLI executions of the same script will find APCu cache empty.
APCu is APC stripped of opcode caching.
The first APCu codebase was versioned 4.0.0, it was forked from the head of the APC master branch at the time.
PHP 7 support is available as of APCu 5.0.0.
APCu can provide a compatibility mode, such that it can provide a drop in replacement for the applicable parts of APC.